1. Field of the Invention
The present invention relates to an analog output buffer circuit and an organic light emitting display using the same.
2. Discussion of Related Art
As the technique relating to thin film transistors has recently been developed together with the development of a semiconductor technique, an active matrix type flat panel display displaying images by using thin film transistors has widely been used. In addition, an organic light emitting display has been developed that has excellent luminous efficiency and brightness, an improved viewing angle, and a rapid response speed.
The organic light emitting display displays images by using a plurality of organic light emitting diodes (OLEDs), wherein the OLED includes an anode electrode, a cathode electrode, and an organic light emitting layer positioned between the anode electrode and the cathode electrode for emitting light by coupling electrons and holes.
The semiconductor layer of the thin film transistor used in the active matrix type flat panel display uses poly-silicon, or the like. However, when using poly-silicon, a process deviation inevitably occurs. If thin film transistors are formed of poly-silicon, a difference in threshold voltage, mobility, and other transistor characteristics for each thin film transistor will occur. Such a difference in the transistor characteristics makes high speed circuit operation difficult and increases component sizes such that the area of the circuit is increased.
FIG. 1 shows a conventional source follower wherein errors occur by threshold voltage Vth in output voltage Vout as compared to input voltage Vin as shown in the following mathematical equation 1.Vout=Vin−Vth  Mathematical Equation 1
FIG. 2 shows a comparator type of an analog output buffer, wherein the output buffer has rapid speed and accuracy with low error. However, the output buffer has disadvantages of a complex structure and high power consumption in implementing the comparator.